Device for minimizing the collection of static electricity on shield for discharging carbon dioxide



Feb. 11, 1964 F. HARTSOCK ETAL 3,

DEVICE FOR MINIMIZING THE COLLECTION OF STATIC ELECTRICITY 0N SHIELD FOR DISCHARGING CARBON DIOXIDE Filed Aug. 12, 1960 W- INENTORS I MW- m A RNEY United States Patent Office 3,121,187 Patented Feb. 11, 1964 The present invention relates to apparatus for discharging and directing carbon dioxide under pressure such as a shield or horn used in connection with a portable fire extinguisher, and, more particularly, to such apparatus and an improved device for minimizing the collection of A static electricity on such shields.

When liquid and/ or gaseous carbon dioxide is passed through a nozzle for converting the same to carbon dioxide snow and/or :gas discharged into a shield constructed of a plastic material, the shield by the inherent nature of its construction will collect a charge of electricity which is capable of giving the operator of the apparatus a disagreeable shock. In the past, apparatus has been devised for eliminating or greatly minimizing the shock to which the operator may be subjected. However, such prior apparatus has been found to be ineffective on the larger sizes of carbon dioxide fire extinguishers, for example, those vvhich discharge fifteen pounds or more of carbon dioxide at a high rate and thus generate a consider-able charge of static electricity on the shield, particularly at low humidity atmospheric conditions.

Accordingly, an object of the present invention is to provide apparatus including a device adapted to be installed in a shield which eliminates or greatly minimizes the collect-ion of static electricity on the shield of large size, high rate extinguishers as well as the shield of smaller size, lower rate extinguishers, wherby ethe operator is not subjected to any perceptible shock regardless of atmospheric humidity conditions.

Another object is to provide such a device which is readily installed in newly fabricated shields and shields of extinguishers already in use.

A further object is to provide such a device which is simple and economical in construction and does not materially increase the cost of the shield.

Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

In accordance with the present invention, it has been discovered that the foreging objects can be generally accomplished by equipping a conventional tubular shield having an open end and a closed end and being constructed of a plastic material inherently subject to collecting a charge of static electricity upon rapid flow of carbon dioxide gas and snow therethrough with metallic prong means secured to the shield adjacent the closed end and extending longitudinally towards the open end and extending adjacently the inner side wall of the shield.

The prong means may be a single prong but static is further minimized by the use of two prongs diametrically opposite each other. Four circumferentially spaced prongs give slight further improvement, but as a practical matter their use is not justified in preference to two prongs.

Further improvement is attained by connecting the prong means in electrical conduction to the conventional metallic nozzle at the closed end of the shield which serves to convert liquid and gaseous carbon dioxide into carbon dioxide snow and gas, and by having the prong or prongs in contact with the inner side wall of the shield throughout their length.

Best results are attained when the prongs have a length about at least one third of the length of the side wall of the shield, but for safety reasons, the prongs should not be longer than about two thirds the length of the side wall so that, when working on an electrical equipment fire, accidental contact between a prong and a live electrical conductor cannot be made. Preferably, the prongs have a length of about three fifths Off the length of the side wall.

Best results are also attained by constructing the prongs of stainless steel strips, rods or wires, the latter being preferred, and providing the prong-s with a point at the free end thereof.

A preferred embodiment of the invention has been chosen for purposes of illustration and description, and is shown in the accompanying drawing, forming a part of the specification, wherein:

FIG. -1 is a fragmentary longitudinal sectional view of apparatus in accordance with the present invention.

FIG. 2 is an enlarged fragmentary sectional view taken substantially along the line 2-2 on FIG. 1, illustrating the manner in which the prong means are secured to the nozzle.

Referring to the drawing in detail, there is shown a tubular shield 10 having an open end 11 and a closed end 12 and having a cylindrical side wall 14, a nozzle 15 within the shield at the closed end thereof, a hose and handle assembly 16 for the shield including a hose 17 connected to the nozzle, and prong means 19 mounted on the nozzle as about to be described.

As shown herein, the prong means 19 is formed of a single unitary piece of wire and comprises a base including a ring or loop 20 and a pair of substantially radial arms 21 extending outwardly from the loop in diametrically opposite directions, and a pointed prong 22 at the.

end of each arm disposed substantially perpendicularly to its arm with each prong extending forwardly in the shield about the same distance and being in contact with the inner side wall 14 of the shield.

The prong means 19 is secured to the shield by placing the loop 20 against an apertured boss 26 of the horn, inserting the exteriorily threaded inner end 25 of the nozzle 15 through the loop, and threading the end of the nozzle into a sleeve 27 of the hose assembly so that a flange 24- on the nozzle overlies the loop and secures the same against the boss.

As a specific example of the present invention, the shield and the prong means may have the following character-istics and dimensions.

Shield:

Material Linear polyethylene. Length of wall 14 15 inches. Thickness of Wall 14 .092 inch. Diameter 4 inches. Weight 0.85 pound.

Nut and nozzle: Material Brass.

Prong means:

Material Stainless steel Wire. Diameter of wire .062 inch. Length of prongs 9 inches.

Five tests were conducted by discharging twenty pounds of carbon dioxide in 12 seconds through the shield equipped with prong means as shown herein, under atmospheric conditions of 60 F. and 20% relative humidity. In each instance, there was no evidence of a charge of static electricity being collected on the shield and the operator could hold the handle and touch the shield without receiving a shock even though the operator was grounded and the fire extinguishing apparatus was insulated from ground.

Five additional tests were conducted with identical apparatus under identical conditions but without the prong means and the shield supported on a bracket. In each instance there was evidence of a charge of static electricity being collected on the shield which manifested itself by a visual glow and discharge of sparks in a dark room. From past tests and experiments, it was obvious that the operator would have received an unpleasant shock had the operator dared to touch the shield.

From the foregoing description, it will be seen that the prong means are highly effective in completely eliminating or greatly minimizing static electricity charges and thereby enabling large high rate portable units to be operated without danger of shock to the operator even under conditions of low humidity. The prong means are readily installed in newly assembled shields as well as shields already in the field.

As various changes may be made in the form, construction and arrangement of the parts herein, without departing from the spirit and scope of the invention, and without sacrificing any of its advantages, it is to be understood that all matter herein is to be interpreted as illustrative and not in any limiting sense.

We claim:

1. Apparatus for discharging and directing carbon dioxide under pressure comp-rising a tubular shield having an open end and a closed end and being constructed of a plastic material inherently subject to collecting a charge of static electricity upon rapid flow of carbon dioxide gas and snow therethrough, a nozzle at said closed end for converting liquid and gaseous carbon dioxide to carbon dioxide gas and snow discharged into said shield, and metallic prong means within said shield and in contact with said nozzle, said prong means extending longitudinally from said closed end towands said open end of said shield and extending adjacently the inner side wall of said shield.

2. Apparatus according to claim 1, wherein said prong means includes a base provided with a ring for mounting said prong means.

3. Apparatus according to claim 2, wherein said shield has a tubular element at its closed end extending through said ring and said nozzle is secured to said element and has a portion overlying said ring to secure said prong means to said shield.

, 4-. Apparatus according to claim 3, wherein said prong means includes a pair of prongs adjacent the inner side wall of said shield.

5. Apparatus according to claim 4, wherein said prongs are diametrically opposite each other.

6. Apparatus according to claim 4, wherein said prongs extend longitudinally for between about one third and about two thirds of the length of the side wall of said shield.

7. Apparatus according to claim 5, wherein said prongs extend longitudinally for about three fifths of the length of the side wall of said shield.

8. Apparatus according to claim 1, wherein said prong means includes a pair of prongs adjacent the inner side Wall of said shield.

9. Apparatus according to claim 8, wherein said prongs are diametrically opposite each other.

10. Apparatus according to claim 8, wherein said prongs extend longitudinally for between about one third and about two thirds of the length of the side wall of said shield.

11. Apparatus according to claim 9, wherein said prongs extend longitudinally for about three fifths of the length of the side wall of said shield.

12. Apparatus according to claim 1, wherein said prong means are in conductive contact with the inner side wall throughout the longitudinal extent of said prong means.

13. A device for minimizing the collection of static electricity on a shield for discharging and directing carbon dioxide under pressure which shield is constructed of a plastic material inherently subject to collecting a charge of static electricity upon rapid flow of carbon dioxide gas and snow therethrough, said device comprising a base having means for mounting said device Within the aforementioned shield and having a pair of radial arms extending in substantially opposite directions from said mounting means, and a prong at the end of each of said arms with each prong disposed substantially perpendicular to said arms and each prong extending in substantially the same direction, the length of each of said prongs being greater than the combined length of said arms, and said prongs being constructed of electrically conductive material.

14. A device for minimizing the collection of static electricity on a shield for discharging and directing carbon dioxide under pressure which shield is constructed of a plastic material inherently subject to collecting a charge of static electricity upon rapid flow of carbon dioxide gas and snow therethrough, said device being constructed of a unitary metallic electrically conductive element and comprising a loop for mounting said device within the aforementioned shield, a pair of substantially radial arms extending in opposite directions from said loop, and a prong at the end of each arm disposed substantially perpendicularly thereto and each prong extending in substantially the same direction with the length of each prong being about the same but being greater than the combined length of said arms.

'15. A device according to claim 14, wherein said pron-gs each have a point at the free end thereof.

References Qited in the file of this patent UNITED STATES PATENTS 1,419,261 Howard June 13, 1922 1,482,642 Dinkela Feb. 5, 1924 2,151,076 Betzler Mar. 21, 1939 

1. APPARATUS FOR DISCHARGING AND DIRECTING CARBON DIOXIDE UNDER PRESSURE COMPRISING A TUBULAR SHIELD HAVING AN OPEN END AND A CLOSED END AND BEING CONSTRUCTED OF A PLASTIC MATERIAL INHERENTLY SUBJECT TO COLLECTING A CHARGE OF STATIC ELECTRICITY UPON RAPID FLOW OF CARBON DIOXIDE GAS AND SNOW THERETHROUGH, A NOZZLE AT SAID CLOSED END FOR CONVERTING LIQUID AND GASEOUS CARBON DIOXIDE TO CARBON DIOXIDE GAS AND SNOW DISCHARGED INTO SAID SHIELD, AND METALLIC PRONG MEANS WITHIN SAID SHIELD AND IN CONTACT WITH SAID NOZZLE, SAID PRONG MEANS EXTENDING LONGITUDINALLY FROM SAID CLOSED END TOWARDS SAID OPEN END OF SAID SHIELD AND EXTENDING ADJACENTLY THE INNER SIDE WALL OF SAID SHIELD. 